An increasing number of disasters (natural and man-made) with a large number of victims and significant social and economical losses are observed in the last years. Although particular events can always be attributed to fate, it is improving the disaster management that have to contribute to decreasing damages and ensuring proper care for citizens in affected areas. In disaster crisis situation, it is of large importance to adequately determine the location of the possible victims and to identify them. This can be carried out on distance using the IR pulsed lasers at certain wavelengths, by registration of the fluorescence and reflection from special infomarkers. The present invention concerns the composite materials that are suitable for such infomarkers as having intense reflection/fluorescence at certain sharp wavelengths.
Near-infrared (700-900 nm) fluorescent compounds are well known in medical diagnostics [Riefke; B.; Semmler; W.; Speck; U.; Hilger; C.-S.; Near infrared imaging agent, U.S. Pat. No. 6,913,743, Jul. 5, 2005.; Changxia S., Jinghe Y., Lei L., Xia W., Yang L., Shufang L., Advances in the study of luminescence probes for proteins, Journal of Chromatography B, 803 (2004) 173-190.; Frangioni, J. V., In vivo near-infrared fluorescence imaging, Current Opinion in Chemical Biology 2003, 7:626-634.]
Also, materials have been proposed for providing intelligible markings that are virtually invisible to the unaided eye on the surface of an article [Acitelli; M. A. et al; Article identification material and method and apparatus for using it, U.S. Pat. No. 4,540,595, Sep. 10, 1985; Andrus; Paul G.; Dolash; T. M.; Providing intelligible markings, U.S. Pat. No. 5,093,147, Mar. 3, 1992; Kamoto; T.; Yamamoto; Y.; Sueyoshi; T.; Fluorescent marking composition and fluorescent mark formed by said composition, U.S. Pat. No. 5,880,176, Mar. 9, 1999.; Strand; M. A. et al: Pigment particles for invisible marking applications, U.S. Pat. No. 6,221,279, Apr. 24, 2001].
It has been shown that the infomarker material can store the information as in 3D memory. In the invention [Rentzepis; P. M. Three-dimensional optical memory, U.S. Pat. No. 5,268,862, Dec. 7, 1993], an active medium, typically a photochromic material and more typically spirbenzopyran, maintained in a three-dimensional matrix, typically of polymer, has been illuminated in selected regions by two UV laser light beams, typically of 532 nm and 1064 nm wavelength, to change from a first, spiropyran, to a second, merocyanine, stable molecular isomeric form by process of two-photon absorption. Regions not temporally and spatially coincidentally illuminated were unchanged. Later illumination of the selected regions by two green-red laser light beams, typically of 1064 nm wavelength each, causes only the second, merocyanine, isomeric form to fluoresce. This fluorescence is detectable by photodetectors as stored binary data. Use of other medium permit the three-dimensional patterning of three-dimensional forms, such as polystyrene polymer solids patterned from liquid styrene monomer. Other examples of conformationally restricted compounds for information storage include aza-bodiby [Zhao, W.; Carreira, E. M.; Conformationally Restricted Aza-Bodipy: A Highly Fluorescent, Stable, Near-Infrared-Absorbing Dye, Angew. Chem. Int. Ed. 2005, 44, 1677-1679.]
A variety of other compounds can be applied as the infomarker infrared fluorescence carriers.
For instance, polymethine dyes (PDs) have been shown to be promising compounds for nonlinear optical applications, such as optical limiting, due to a strong and broad excited-state absorption (ESA) in the visible region. It is relatively easy to modify the PDs structure using different heterocyclic terminal groups, different lengths of the polymethine chain, and introduction of specific substitutes into the polymethine chain and cyclization of the chain by conjugated or unconjugated bridges [Kachkovski O D, Tolmachov O I, Slominskii Y L, Kudinova M O, Derevyanko N O, Zhukova O O, Electronic properties of polymethine systems 7: soliton symmetry breaking and spectral features of dyes with a long polymethine chain, DYES AND PIGMENTS 64 (3): 207-216 March 2005; Kachkovski A D, Zhukova O O, Electronic properties of polymethine systems. 6. Bond order and bond length changes upon excitation, DYES AND PIGMENTS 63 (3): 323-332 December 2004; Lepkowicz R S, Cirloganu C M, Przhonska O V, Hagan D J, Van Stryland E W, Bondar M V, Slominsky Y L, Kachkovski A D, Mayboroda E I, Absorption anisotropy studies of polymethine dyes, CHEMICAL PHYSICS 306 (1-3): 171-183 Nov. 15, 2004; {hacek over (S)}imon P, Landl M, Breza M, Kvasnik F, New NIR dyes for ammonia sensing, SENSORS AND ACTUATORS B-CHEMICAL 90 (1-3): 9-14 Sp. Iss. SI, Apr. 20, 2003].
Aromatic imides are known to be electrochromic with intense UV-vis absorptions in their neutral states. These imides exhibit bathochromic shifts to a longer wavelength toward the near infrared (NIR) region when they undergo one-electron reductions. Accordingly, the introduction of chiral centers into aromatic imides would allow for the detection and analysis of these chromophores using techniques dependent upon their optical activity, such as circular dichroism (CD) [Todd E K, Wang S, Wan X H, Wang Z Y, Chiral imides as potential chiroptical switches: synthesis and optical properties, TETRAHEDRON LETTERS 46 (4): 587-590 Jan. 24, 2005; Adams D J, Blake A J, Cooke P A, Gill C D, Simpkins N S, Highly enantioselective synthesis of chiral imides and derived products via chiral base desymmetrisation, TETRAHEDRON 58 (23): 4603-4615 Jun. 3, 2002].
Because the metal complexes of porphyrazines exhibit high fluorescence yield in the infrared (IR) region, their fluorescent changes in the photochromic process could be used as a sensitive binary optical readout [Luo Q F, Cheng S H, Tian H, Synthesis and phototropism of a new binuclear porphyrazinato magnesium(II), TETRAHEDRON LETTERS 45 (41): 7737-7740 Oct. 4 2004].
Rare earth metal complexes, especially Eu3+ complexes with organic ligands or a constituent in nanoparticles, characterise intensive florescence in infrared region. [Diamente, P. R.; van Veggel, F. C. J. M., Water-Soluble Ln3+-doped LnF3 Nanopartcles: Retention of Strong Luminescence and Potential as Biolabels, Journal of Fluorescence, Vol. 15, No. 4, 543-551 July 2005.; Lenaerts P, Ryckebosch E, Driesen K, Van Deun R, Nockemann P, Groller-Walrand C, Binnemans K, Study of the luminescence of tris (2 thenoyltrifluoroacetonato) lanthanide(III) complexes covalently linked to 1,10-phenanthroline-functionalized hybrid sol-gel glasses, JOURNAL OF LUMINESCENCE 114 (1): 77-84 July 2005.; Klink S I, Alink P O, Grave L, Peters F G A, Hofstraat J W, Geurts F. van Veggel FCJM, Fluorescent dyes as efficient photosensitizers for near-infrared Nd3+, JOURNAL OF CHEMICAL SOCIETY-PERKIN TRANSACTIONS 2 (3): 363-372 2001.; Bakker B H, Goes M, Hoebe N, van Ramesdonk H J, Verhoeven J W, Werts M H V, Hofstraat J W Luminescent materials and devices: lanthanide azatriphenylene complexes and electroluminescent charge transfer systems, COORDINATION CHEMISTRY REVIEWS 208: 3-16 Oct. 2000.; Wolbers M P O, vanVeggel F C J M, Hofstraat J W, Guerts F A J, Reinhoudt D N, Luminescence properties of m-terphenyl-based Eu3+ and Nd3+ complexes: visible and near-infrared emission JOURNAL OF THE CHEMICAL SOCIETY-PERKIN TRANSACTIONS 2 (11): 2275-2282 November 1997.] It is important to notice that the ions of lanthanides neodymium (Nd3+) and erbium (Er3+) adapt ideally as fluorescing ingredient, because they have inner 4 f gradations according to 1330 nm and 1550 nm. In general, the ions of lanthanides dissolve in organic solvents and in polymers relatively badly, then they ions beforehand encapsulate with organic ligands, to increase their contribution.
Some of the most promising materials for IR fluorescence are the electrically conductive conjugated organic polymers. For example, aryl amine polymers show, among their optical properties, photoluminescence in their reduced state, which is quenched when the polymer is oxidized. There are few studies concerning the photoluminescence of polyaniline (PANI) and similar materials [Akther H, Bhuiyan A H, Infrared and ultra violet-visible spectroscopic investigation of plasma polymerized N,N,3,5-tetramethylaniline thin films, THIN SOLID FILMS 474 (1-2): 14-18 Mar. 1, 2005; Antonel P S, Andrade E M, Molina F V, Potential and film thickness dependence of the photoluminescence of aryl amine polymers, ELECTROCHIMICA ACTA 49 (22-23): 3687-3692 Sep. 15, 2004]. Most of the polyamine polymers can be applied also as NIR sensing materials [Christie S, Scorsone E, Persaud K, Kvasnik F, Remote detection of gaseous ammonia using the near infrared transmission properties of Polyaniline, SENSORS AND ACTUATORS B-CHEMICAL 90 (1-3): 163-169 Sp. Iss. S I, Apr. 20, 2003; Scorsone E, Christie S, Persaud K C, Kvasnik F, Evanescent sensing of alkaline and acidic vapours using a plastic clad silica fibre doped with poly(o-methoxyaniline), SENSORS AND ACTUATORS B-CHEMICAL 97 (2-3): 174-181 Feb. 1, 2004].